An organic EL (Electroluminescence) display device is represented as an example of a display device. An organic EL display device has a plurality of pixels formed over a substrate and includes an organic light-emitting element (hereinafter, referred to as a light-emitting element) in each of the plurality of pixels. A light-emitting element possesses a layer (hereinafter, referred to as an organic layer or an EL layer) including an organic compound between a pair of electrodes (cathode and anode) and is operated by supplying current between the pair of electrodes. Color provided by a light-emitting element is mainly determined by a light-emitting material in an EL layer, and light emission with a variety of colors can be obtained by appropriately selecting a light-emitting material. Arrangement of a plurality of light-emitting elements giving different colors on a substrate makes it possible to reproduce a full-color image.
Emission color of a light-emitting element can also be adjusted by utilizing a light-interference effect in a light-emitting element. For example, it is disclosed in Japanese Patent Application Publications No. 2013-51155 and 2009-187748 that an optical adjustment layer is provided to one of the electrodes of a light-emitting element to control resonance of light emitted from the light-emitting element, thereby adjusting emission intensity and emission color.